Experts agree that long-term climate change is occurring and that it is already affecting California’s water resources.
Warming temperatures, changing rain and snowfall patterns and rising sea levels will profoundly affect the state’s ability to manage water supplies and other natural resources.
Adapting the state’s water system to these changes will be a significant challenge in the coming decades.
Winter snowpack in the Sierra Nevada – the backbone of the state’s water supply – is expected to decline significantly as temperatures rise. New climate models suggest the snowpack will shrink by at least 25% by 2050, a major blow to the state’s built-in water storage system and the man-made delivery system built over the past 50 years to capture and deliver snowmelt.
In addition, the snowpack is expected to peak earlier and melt faster in the future. More precipitation is expected to fall as rain rather than snow, raising the specter of higher peak flood flows and additional strain on the state’s fragile levees and flood control systems.
A state climate report issued in April 2009 found that changing precipitation patterns will “result in longer and drier droughts and decreased groundwater levels, coupled with a higher frequency and severity of extreme flooding events.” In some years, the report said, water levels in reservoirs such as Lake Oroville, Folsom Lake and Lake Shasta could fall below outtake levels, effectively ending reservoir releases until storage levels recovered
Sea Level Rise
Sea level as measured at the Golden Gate has risen more than six inches since the early 20th century. Models predict a median rise of another 1.6 feet over the 21st century due to climate change.
In the Delta, some researchers believe sea level could rise as much as 12-16 inches over the coming decades.
Sea level rise would have a serious effect on the Delta. It could disrupt ecosystems, undermine wetlands restoration efforts, and put even more pressure on the Delta’s fragile levee system, putting at risk the water supply for about 22 million Californians and millions of acres of irrigated farmland.
Some models show that a single-foot rise in sea level in the Delta would increase the frequency of extremely high tides in the Western Delta and increase salinity intrusion from the ocean, degrading freshwater supplies exported from the Delta unless more fresh water is released from upstream reservoirs. Coastal aquifers also could be threatened.